Stepwise decrease in moxifloxacin susceptibility amongst clinical isolates of multidrug-resistant Mycobacterium tuberculosis: correlation with ofloxacin susceptibility.

To study the effectiveness of moxifloxacin (MOX) against multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB), in vitro drug susceptibility tests on MOX and ofloxacin (OFX) using the MGIT system against 132 nonduplicate MDR MTB isolates (108 OFX-sensitive and 24 OFX-resistant) were performed. Eleven OFX-resistant non-MDR MTB isolates were also included. All strains that were susceptible to OFX were shown to be also susceptible to MOX. For OFX-resistant isolates, regardless of their MDR status, a 4- to 8-fold decrease in MIC was observed for MOX when compared to OFX. On the basis of similarities in mode of action and pharmacokinetic data between MOX and OFX, a breakpoint MIC of 2 mg/L was suggested for MOX in the MGIT system. All but two OFX-resistant isolates possessed MIC of MOX of 2 mg/L or lower and were considered to be susceptible to MOX; however, all OFX-resistant strains studied had mutations involved in resistance to quinolones. DNA sequence analysis for the gyrase A mutation, which was an indicator for OFX resistance, correlated with MOX susceptibility changes. Significant decreases in MOX susceptibility amongst MDR-MTB strains were observed that correlated with OFX susceptibility. The Asp94Gly mutation appeared to be associated with a higher level of MICs to both OFX and MOX. These findings on the stepwise decline of in vitro susceptibility to MOX suggest that clinical usage of MOX should be accompanied by careful monitoring of susceptibility to this important anti-MDR MTB drug.

A fatal case of Chromobacterium violaceum septicemia in Hong Kong.

Chromobacterium violaceum causes a rare infection in human, usually in tropical or subtropical areas. We report a fatal case of C. violaceum infection affecting a 40-year-old previously healthy man in Hong Kong. He presented with a wound infection and lymphadenitis. Despite multiple antibiotic treatment, including ciprofloxacin, he succumbed shortly after admission to the hospital. We report the epidemiological investigation findings and discuss the possible sources of infection. Physicians should be alert to this rare but fatal infection. Injury prevention and proper wound care should be emphasized to the public.

Molecular subtyping of Vibrio cholerae O1 and O139 by pulsed-field gel electrophoresis in Hong Kong: correlation with epidemiological events from 1994 to 2002.

Two hundred twenty isolates of Vibrio cholerae O1 and O139 collected from 1994 to 2002 in Hong Kong were analyzed by pulsed-field gel electrophoresis (PFGE). Chromosomal DNAs from all V. cholerae isolates in agarose plugs were digested with the restriction enzyme NotI, resulting in 20 to 27 bands. Sixty distinctive PFGE patterns in the range of 10 to 300 kb were noted among 213 isolates typeable by PFGE. By comparing the common PFGE patterns obtained from four well-defined outbreaks of V. cholerae O1 and O139 with those obtained from other, epidemiologically unrelated isolates during the study period, indistinguishable and similar PFGE patterns were identified, indicating their close relatedness, in agreement with the results of epidemiological investigations. Heterogeneous PFGE patterns (with four to six banding differences), however, were identified among strains that were imported from other parts of Asia, including Indonesia, India, and Pakistan. Correlations with epidemiological information further support the usefulness of PFGE as an epidemiological tool in laboratory investigations of suspected outbreaks. Standardization of PFGE methodology will allow international comparison of fingerprint patterns and will form the basis of a laboratory network for tracking V. cholerae.